Preventing childhood asthma: Could gut bacteria be the key?

A study finds that asthma passing from mother to child may not solely be down to genetics; gut bacteria seem to play a pivotal role, too. Probiotics could, in the future, prevent some cases of infant asthma.

A new study investigates the link between asthma and gut bacteria.

Asthma is a relatively common condition that affects around 13 percent of pregnant women.

During pregnancy, symptoms can get worse, and poor symptom control is tied to lower birth weights. This effect is particularly pronounced in male babies.

Also, if a pregnant mother's asthma is not well-controlled during pregnancy, her offspring are more likely to develop asthma. This hints that there is more to the interaction than genes alone: in utero changes must also be taking place.

In recent years, our gut bacteria, or microbiome, have received a lot of attention, being called into the spotlight for a whole host of conditions. They have been implicated in conditions as diverse as type 1 diabetes and schizophrenia, and now, infant asthma is in focus.

The microbiome and infant asthma

A team of researchers — led by AllerGen investigator and UAlberta microbiome epidemiologist Anita Kozyrskyj — set out to look at the interaction between asthma during pregnancy and gut bacteria. Their results were recently published in the European Respiratory Journal.

The researchers recruited 1,000 mothers and their infants to the AllerGen's Canadian Healthy Infant Longitudinal Development Study. At 3–4 months of age, the infants' fecal microbiota were assessed and compared with samples from mothers without asthma.

They found that Caucasian baby boys whose mothers had asthma were one third more likely to have a gut microbiome with specific characteristics at the age of 3–4 months.

"We saw a significant reduction in the family of microbes called Lactobacillus in Caucasian baby boys born to pregnant women who had asthma, and this was especially evident if the asthmatic mother had allergies or was overweight."

Anita Kozyrskyj

This change of the microbiome has previously been attributed to other factors. For instance, it could be that asthmatic mothers are more likely to be prescribed antibiotics or have cesarean delivery births, both of which have the potential to alter the makeup of the baby's gut bacteria.

The analysis in this study controlled for these factors, alongside pre-pregnancy weight, whether or not the baby was breast-fed, ethnicity, and maternal allergies.

Even after accounting for these factors, Lactobacillus levels were lower in the guts of 3- to 4-month-old babies of asthmatic mothers. Levels were particularly low in children of overweight mothers and those with allergies.

Future prevention of childhood asthma

For the first time, scientists have uncovered evidence that changes in gut bacteria could be the result of maternal asthma during gestation. Kozyrskyi explains the importance of the findings:

"Our discovery, with more research, could eventually lead to a preventative approach involving modifying the gut microbiome in infants to reduce the risk."

Interestingly, asthma during pregnancy influenced female infants' gut bacteria differently. "Baby girls," says Kozyrskyj, "were more likely to have higher amounts of bacteria in the Bacteroidaceae family, which are important for maintaining the mucous barrier that protects gut cells from damage by harmful substances. So, this change may actually benefit female babies' health.

The authors believe that this difference in microbiome might be why female babies are less likely to develop asthma at an early age. However, they may still be more likely to develop asthma during puberty.

The researchers mention some shortfalls of the study design. For instance, asthma was rated in questionnaires by the mothers, rather than by doctors.

But because the study involved a relatively large number of participants, the authors conclude, "Our results provide the first evidence of a programming effect of prenatal maternal asthma on gut microbial composition that is independent of birth and postnatal events."

The findings offer the intriguing possibility that one day, infant asthma could be prevented in some cases simply by administering probiotics. Of course, more work will need to be done before this simple intervention can come into play.

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